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RESEARCH ARTICLE Open Access

Combined pars plana glaucoma drainagedevice placement and vitrectomy using avitrectomy sclerotomy site for tubeplacement: a case seriesEnchi Kristina Chang1, Sanchay Gupta1, Marika Chachanidze2, John B. Miller1, Ta Chen Chang3 andDavid A. Solá-Del Valle1*

Abstract

Purpose: The purpose of this study is to report the safety and efficacy of pars plana glaucoma drainage deviceswith pars plana vitrectomy using one of the vitrectomy sclerotomy sites for tube placement in patients withrefractory glaucoma.

Methods: Retrospective case series of 28 eyes of 28 patients who underwent combined pars plana glaucomadrainage device and pars plana vitrectomy between November 2016 and September 2019 at Massachusetts Eyeand Ear. Main outcome measures were intraocular pressure (IOP), glaucoma medication burden, best correctedvisual acuity, and complications. Statistical tests were performed with R and included Kaplan-Meier analyses,Wilcoxon paired signed-rank tests, and Fisher tests.

Results: Mean IOP decreased from 22.8 mmHg to 11.8 mmHg at 1.5 years (p = 0.002), and mean medication burdendecreased from 4.3 to 2.1 at 1.5 years (p = 0.004). Both IOP and medication burden were significantly lower at allfollow-up time points. The probability of achieving 5 < IOP ≤ 18 mmHg with at least 20% IOP reduction frompreoperative levels was 86.4% at 1 year and 59.8% at 1.5 years. At their last visit, three eyes (10.7%) achievedcomplete success with IOP reduction as above without medications, and 14 eyes (50.0%) achieved qualified successwith medications. Hypotony was observed in 1 eye (3.6%) prior to 3 months postoperatively and 0 eyes after 3months. Visual acuity was unchanged or improved in 23 eyes (82.1%) at their last follow-up. Two patients had avisual acuity decrease of > 2 lines. Two eyes required subsequent pars plana vitrectomies for tube obstruction, andone eye had transient hypotony.

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* Correspondence: [email protected] Eye and Ear, Department of Ophthalmology, Harvard MedicalSchool, Boston, MA, USAFull list of author information is available at the end of the article

Chang et al. BMC Ophthalmology (2021) 21:106 https://doi.org/10.1186/s12886-021-01872-z

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Conclusions: The results of pars plana glaucoma drainage device and pars plana vitrectomy using one of thevitrectomy sclerotomy sites for tube placement are promising, resulting in significant IOP and medication-burdenreductions through postoperative year 1.5 without additional risk of postoperative complications. Insertingglaucoma drainage devices into an existing vitrectomy sclerotomy site may potentially save surgical time byobviating the need to create another sclerotomy for tube placement and suture one of the vitrectomy ports.

Keywords: Glaucoma, Pars plana, Pars plana glaucoma drainage device, Pars plana vitrectomy, Ahmed drainageimplant, Baerveldt drainage implant, Safety, Efficacy

BackgroundGlaucoma drainage devices (GDDs) are increasingly usedin the treatment of glaucoma refractory to medical ther-apy or after unsuccessful trabeculectomy or laser proce-dures. Between 1995 and 2004, the use of GDDsincreased by 184% in Medicare patients alongside a 53%decrease in the number of trabeculectomies in eyes with-out scarring [1]. GDDs may be inserted into the anteriorchamber, sulcus, or pars plana depending on comorbidocular pathology that may preclude placement in a par-ticular location or if a vitrectomy is needed for retinalpathology. Namely, tube placement in the anteriorchamber may not be recommended in the setting ofsome corneal diseases, iridocorneal angle abnormalities,or peripheral anterior synechiae, amongst other patholo-gies [2]. In these cases, tube placement in the pars plana(PP) may be considered to prevent postoperative anter-ior chamber complications [3]. PP GDD insertion re-quires concurrent or prior pars plana vitrectomy (PPV)to prevent vitreous occlusion of the tube. In the com-bined PPV and PP GDD surgery, treatment of concur-rent posterior segment diseases may also be performed,minimizing the need for multiple separate surgicalprocedures.During combined PPV and pars plana GDD place-

ment, the GDD tube may be inserted into a new scler-otomy or an existing sclerotomy used for one of thevitrectomy ports [4, 5]. With prior 20-gauge scleroto-mies for PPV, concerns regarding the risk of hypotonyfrom leakage around the tube led to greater adoption ofcreating a new sclerotomy for the tube. In fact, tube in-sertion into sclerotomies larger than 21-gauge was sug-gested to be associated with higher leakage rates [6].Thus, the vitrectomy sclerotomies were closed with su-turing to allow for a watertight closure, and a new, sep-arate sclerotomy was created for the GDD tube.With modern small-gauge (i.e. 23- and 25-gauge)

PPVs, however, there may be a lower risk of hypotonyfrom leakage around a tube inserted into a preexistingsclerotomy [3, 7]. Utilizing an existing sclerotomy alsolikely saves surgical time by eliminating the need to cre-ate another sclerotomy and suture one of the port sites,which may result in less inflammation by minimizing

the amount of suture material in the sclera. To the bestof our knowledge, prior studies have not examined thesafety and efficacy of inserting GDDs into an existingsclerotomy utilized by the small-gauge PPVs, thus elim-inating the need for creating a new sclerotomy for thetube. In this study, we evaluate the surgical outcomesand complication rates of pars plana GDD placementwith tube insertion into one of the existing 23- or 25-gauge vitrectomy sclerotomy sites in patients with re-fractory glaucoma.

MethodsStudy designThis is a retrospective cohort study of consecutive adultglaucoma patients who underwent PP GDD insertionwith PPV using one of the vitrectomy sclerotomy sitesfor tube insertion. After receiving approval from theMass General Brigham Institutional Review Board, med-ical records of patients who underwent the procedurebetween April 2016 and November 2019 at Massachu-setts Eye and Ear were identified and reviewed. GDD in-sertion was performed by 9 different providers, and PPVwas performed by 8 different providers. Data collectionabided by the Declaration of Helsinki and the HealthPortability and Accountability Act. Patients were in-cluded if they met the following criteria: (1) diagnosis ofglaucoma; (2) concurrent PP GDD surgery and PPV withtube insertion into one of the vitrectomy sclerotomysites; (3) at least 3 months of follow-up; and (4) age ≥ 18years. If patients had undergone procedures in both eyes,the left eye was included in our study.Demographic and preoperative data included patient

age, gender, glaucoma diagnosis and stage, previous ocu-lar surgeries, IOP, number of glaucoma medications, andvisual acuity (VA). Glaucoma stages were defined as cir-cumpapillary retinal nerve fiber layer thinning on opticalcoherence tomography with Humphrey visual field find-ings of no abnormalities for mild glaucoma; a single cor-responding inferior or superior deficit for moderateglaucoma; or a combination of paracentral or superiorand inferior defects for severe glaucoma [8]. An indeter-minate stage was defined if visual field testing could notbe performed reliably or if the patient had light

Chang et al. BMC Ophthalmology (2021) 21:106 Page 2 of 14

perception or no light perception vision. IOP was mea-sured with Goldmann applanation tonometry. Preopera-tive IOP, medication burden, and VA were calculated asan average of the values from two consecutive visitsprior to the procedure. Postoperative data were collectedat 1 day (POD1), 2 weeks (POW2), 6 weeks (POW6), 3months (POM3), 6 months (POM6), 1 year (POY1), and1.5 years (POY1.5) after surgery. At each time point, the

Table 1 Demographic characteristics and preoperative data ofglaucoma patients who underwent pars plana glaucomadrainage device implantation with pars plana vitrectomy usingthe vitrectomy sclerotomy for tube insertion

Parameters

Demographics

Eyes 28

Female Eyes, N (%) 15 (53.6)

Age (years)

Mean ± SD 61.9 ± 20.2

Range 18–90

Glaucoma Stage, N (%)

Mild 4 (14.3)

Moderate 7 (25.0)

Severe 15 (53.6)

Indeterminate 2 (7.1)

Glaucoma Type, N (%)

Aphakic 1 (3.6)

Chronic angle closure 9 (32.1)

Mixed mechanisma 7 (25.0)

Neovascular 1 (3.6)

Primary open angle 6 (21.4)

Pseudoexfoliation 4 (14.3)

Prior Surgeries, N (%)

None 5 (17.9)

AGI 3 (10.7)

Anterior vitrectomy 3 (10.7)

DSEK/DSAEK 4 (14.3)

KPro 3 (10.7)

iStentb 1 (3.6)

Phaco 20 (71.4)

PKP 2 (7.1)

PPV 8 (28.6)

Trabeculectomy 4 (14.3)

Other (OGI repair, GSL, EL) 7 (25.0)

Prior Glaucoma Laser, N (%)

None 8 (28.6)

ALT 1 (3.6)

LTP 1 (3.6)

LPI 5 (17.9)

MPCPC/CWCPC 10 (35.7)

SLT 3 (10.7)

PRP 1 (3.6)

YAG 3 (10.7)

Preoperative Baseline

IOP (mmHg)

Mean ± SD 22.8 ± 7.3

Table 1 Demographic characteristics and preoperative data ofglaucoma patients who underwent pars plana glaucomadrainage device implantation with pars plana vitrectomy usingthe vitrectomy sclerotomy for tube insertion (Continued)Parameters

Range 10.5–38

# of Glaucoma Medications

Mean ± SD 4.3 ± 1.0

Range 2–6

Visual Acuity (LogMAR)

Mean ± SD 0.94 ± 0.96

Range 0–3

Surgical Indications, N (%)

Aphakia 6 (21.4)

ACIOL 5 (17.9)

Chronic angle-closure glaucoma 9 (32.1)

DSEK/DSAEK 4 (14.3)

KPro 3 (10.7)

Vitreous prolapse 3 (10.7)

Lens fragment in vitreous 2 (7.1)

PDR with VH 3 (10.7)

Hypertensive retinopathy with VH 1 (3.6)

Type of Procedure, N (%)

AGI / PPV 24 (85.7)

BGI / PPV 4 (14.3)

PPV Gauge, N (%)

23G 9 (32.1)

25G 19 (67.9)

N number of eyes, SD standard deviation, IOP intraocular pressure, mmHgmillimeters of mercury, LogMAR logarithm of the minimum angle of resolution,AGI Ahmed glaucoma implant, BGI Baerveldt glaucoma implant, PPV parsplana vitrectomy, ALT argon laser trabeculoplasty, LTP laser trabeculoplasty, LPIlaser peripheral iridotomy, MPCPC micropulse cyclophotocoagulation, CWCPCcontinuous wave cyclophotocoagulation, SLT selective laser trabeculoplasty,PRP panretinal photocoagulation, YAG YAG capsulotomy, DSEK Descemetstripping endothelial keratoplasty, DSAEK Descemet stripping automatedendothelial keratoplasty, KPro keratoprosthesis, Phaco phacoemulsification, PKPpenetrating keratoplasty, OGI open globe injury, GSL goniosynechialysis, ELendolaser, ACIOL anterior chamber intraocular lens, PDR proliferative diabeticretinopathy, VH vitreous hemorrhageaMixed mechanism glaucoma includes a combination of primary open angle,chronic angle closure, steroid response, pseudoexfoliative, traumatic, uveitic,and neovascular glaucoma as well as glaucoma secondary to an iris melanomaor corneal transplantationbiStent Trabecular Micro-Bypass Stent (Models GTS100R and GTS100L, GlaukosCorporation, San Clemente, California); and iStent inject® Trabecular Micro-Bypass System (Model G2-M-IS, Glaukos Corporation, San Clemente, California)


IOP, number of glaucoma medications, VA, duration offollow-up, subsequent IOP-lowering procedures, and thepresence of postoperative complications such as inflam-mation in the anterior chamber, hypotony, cornealedema, cystoid macular edema (CME), vitreoushemorrhage, and tube obstruction were recorded. Glau-coma medication burden was obtained at each visit bymanually counting the number of individual glaucomamedications used by the patient at that time, with medi-cations composed of two IOP-lowering compounds re-corded as two medications.

Surgical procedureThe procedures were performed by multiple glaucomaand retina specialists. All patients underwent eitherAhmed (New World Medical, Rancho Cucamonga, CA,USA) or Baerveldt (Johnson & Johnson Vision, SantaAna, CA, USA) GDD implant placement with 23- or 25-gauge vitrectomy. The type of glaucoma implant and vi-trectomy gauge were at the surgeons’ discretion. For pa-tients with preexisting vitreous hemorrhage orneovascular glaucoma, intravitreal injections were ad-ministered preoperatively at the retina surgeon’s discre-tion. A retrobulbar block was placed by anesthesia, andthe operative eye was prepared in the standard ophthal-mic fashion. A conjunctival peritomy was created, andsub-Tenon’s space was accessed. The GDD implant wasplaced and secured to the sclera with 2 interrupted 8–0nylon sutures. If an Ahmed glaucoma drainage devicewas used, the tube was first primed with balanced saltsolution to open and wet the valve leaflets. If a Baerveldtglaucoma drainage device was used, an external ligationwith absorbable suture around the tube was applied. Forthe vitrectomy, trocars were used to place cannulas inthe inferotemporal, superotemporal, and superonasalquadrants through the pars plana in a beveled fashion. A4mm infusion cannula was placed through the infero-temporal cannula, and a complete standard three-portPPV was performed. The inferotemporal and superona-sal sclerotomies were sutured using 7–0 polyglactin su-tures in an interrupted fashion, and the conjunctiva wasclosed in conjunction with the sclerotomy closure. Thesuperotemporal sclerotomy was then used for GDD tubeplacement. The tube was then cut at the appropriatelength, bevel down. The superotemporal trocar was thenremoved. If an Ahmed glaucoma drainage device wasplaced, approximately 0.3 mL of a dispersive ophthalmicviscosurgical device was injected into the pars plana oranterior chamber to prevent hypotony. The tube wasthen inserted into the pars plana. A cadaveric cornealpatch graft was used to cover the tube and secured tothe sclera with 2 interrupted 7–0 polyglactin sutures.The overlying Tenon’s and conjunctiva were secured atthe limbus using interrupted and running 8–0

Table 2 Intraocular pressure, medication burden, and visualacuity outcomes data at different time points for glaucomapatients who underwent pars plana glaucoma drainage deviceimplantation with pars plana vitrectomy using the vitrectomysclerotomy for tube insertion

IOP(mmHg)

Medications VA(LogMAR)a

Preoperative (n = 28)

Mean (SD) 22.8 (7.3) 4.3 (1.0) 0.94 (0.96)

1 day (n = 27)

Mean (SD) 10.1 (4.9) 0.0 (0.0) 1.32 (0.80)

Decrease frombaseline

12.2 (8.9) 4.3 (1.0) −0.39 (0.86)

p value < 0.001* < 0.001* 0.031*

2 weeks (n = 27)

Mean (SD) 12.6 (5.2) 0.7 (1.2) 1.06 (0.89)


10.3 (9.7) 3.6 (1.4) −0.20 (0.96)

p value < 0.001* < 0.001* 0.280

6 weeks (n = 27)

Mean (SD) 14.3 (6.5) 1.4 (1.5) 0.75 (0.69)


8.9 (7.8) 2.9 (1.5) 0.21 (0.75)

p value < 0.001* < 0.001* 0.211

3 months (n = 25)

Mean (SD) 13.2 (4.4) 1.7 (1.5) 0.80 (0.82)


10.4 (7.9) 2.6 (1.3) 0.17 (0.84)

p value < 0.001* < 0.001* 0.486

6 months (n = 24)

Mean (SD) 13.2 (3.9) 2.0 (1.4) 0.84 (0.82)


10.2 (7.6) 2.2 (1.4) 0.20 (0.98)

p value < 0.001* < 0.001* 0.433

1 year (n = 22)

Mean (SD) 13.1 (4.2) 1.9 (1.3) 0.74 (0.78)


9.4 (8.3) 2.2 (1.4) 0.12 (1.03)

p value < 0.001* < 0.001* 0.570

1.5 years (n = 12)

Mean (SD) 11.8 (3.2) 2.1 (1.2) 0.45 (0.38)


7.7 (5.6) 2.1 (1.2) 0.57 (1.03)

p value 0.002* 0.004* 0.185

IOP intraocular pressure, mmHg millimeters of mercury, VA visual acuity,LogMAR logarithm of the Minimum Angle of Resolution, n number of eyes, SDstandard deviationaPatients with LP or NLP at these time points were excluded in mean and pvalue calculations due to a lack of a validated LogMAR equivalent.*Indicates significant p value < 0.05


Fig. 1 Line graph of average values of postoperative (a) intraocular pressure, (b) number of medications, and (c) visual acuity over time forglaucoma patients who underwent pars plana glaucoma drainage device implantation with pars plana vitrectomy using the vitrectomysclerotomy for tube insertion. Error bars denote standard deviation of the mean


polyglactin sutures. A sample video of the surgical pro-cedure is included in the references [9].

Outcome measuresPrimary outcome measures were IOP reduction, glau-coma medication burden, VA, cumulative success prob-abilities from Kaplan-Meier (KM) analyses, complicationrates, and need for additional glaucoma surgery. Successcriteria were obtained from the Tube Versus Trabecu-lectomy Study [10], with the addition of a more-stringent IOP criteria as follows. Success was defined asan IOP reduction ≥ 20% from preoperative IOP withouthypotony and (Criteria 1) IOP ≤ 21mmHg; (Criteria 2)IOP ≤ 18 mmHg; or (Criteria 3) IOP ≤ 14 mmHg. Hy-potony was defined as IOP ≤ 5 mmHg. A failure was re-corded if a patient did not meet the specified successcriteria on two consecutive follow-up visits after 3months, required additional glaucoma surgery or laserprocedure, or developed no light perception (NLP) vi-sion. Patients who required an additional non-glaucomaprocedure were censored from survival analysis.Patients were recorded as a complete success if they

satisfied Criteria 1 without medications; qualified successif they satisfied Criteria 1 with medications; and qualifiedfailure if they did not meet the above criteria for successbut did not require additional glaucoma surgery or de-velop NLP vision at their last visit.

Statistical analysisStatistical analyses were performed using R (version4.0.2). A p value < 0.05 was considered statistically sig-nificant. Average and standard deviation (SD) were cal-culated for IOP, medication burden, and VA. Linegraphs of average values were generated with error barsrepresenting standard deviation. Comparisons with pre-operative values were conducted with Wilcoxon pairedsigned-rank tests. Kaplan-Meier analyses were used togenerate cumulative success probabilities, with successcriteria as defined above. Hazard ratios for preoperativeand demographic characteristics were obtained fromCox proportional hazard regression analyses. Snellen vis-ual acuities were converted to logarithm of minimumangle of resolution (LogMAR) equivalents, with values of2 and 3 representing count fingers and hand motion vi-sion, respectively. Patients with light perception or nolight perception vision were not converted to logMARequivalents and excluded from mean calculations andpaired Wilcoxon testing.

ResultsA total of 28 eyes of 28 glaucoma patients were includedin this study. Patient demographic and preoperative dataare presented in Table 1. Mean ± SD age was 61.9 ± 20.2(range 18–90), and 53.6% of the patients were female.

Most patients (53.6%) had severe glaucoma, and themost common glaucoma type was chronic angle-closureglaucoma (32.1%) followed by mixed mechanism (25.0%)and primary open-angle glaucoma (21.4%). The meanpreoperative IOP was 22.8 ± 7.3 mmHg (range 10.5–38mmHg) with a medication burden of 4.3 ± 1.0 (range 2–6). The mean follow-up time was 17.7 ± 7.7 (range 5.9–35.5 months). The most common surgical indications forthe combined procedure were chronic angle-closureglaucoma with synechiae (32.1%), aphakia with vitreousin the anterior chamber (21.4%), and an anterior cham-ber intraocular lens (17.9%). For the aphakic eye withvitreous in the anterior chamber, a secondary intraocularlens was not implanted during surgery. The GDD wasinserted into an existing sclerotomy site used for the vi-trectomy in all eyes.The type of implant and PPV gauge are listed in Table

1. Twenty-four eyes (85.7%) received an Ahmed glau-coma implant, and the remaining 4 eyes (14.3%) receiveda Baerveldt glaucoma implant. A 25G vitrectomy wasperformed in 19 eyes (67.9%) and 23G vitrectomy in 9eyes (32.1%).Postoperative intraocular pressure, medication burden,

and visual acuity outcomes are summarized in Table 2.Line graphs of postoperative outcomes are shown inFig. 1. IOP was significantly decreased at all follow-uptime points compared to preoperative levels, with anaverage reduction of 7.7 ± 5.6 mmHg at POY1.5 (p =0.002). Medication burden was also significantly de-creased at all time points with an average of 2.1 ± 1.2 atPOY1.5 (p = 0.004). VA was unchanged from preopera-tive levels at all time points after POD1. VA was thesame or improved at the last follow-up visit for 23 eyes(82.1%), with the remaining 5 eyes (17.9%) experiencingdecreased vision. One eye experienced VA loss by 1 line,2 eyes by 2 lines, and 2 eyes by > 2 lines. One eye thatexperienced VA loss of > 2 lines had previously

Table 3 Cumulative success probabilities at different timepoints based on Kaplan-Meier survival analyses

Cumulative Success (%) ± SE (95% Confidence Interval)

IOP reduction ≥ 20% with IOP > 5mmHg and

IOP ≤ 21mmHg IOP ≤ 18mmHg IOP ≤ 14mmHg

3months 100.0 ± 0.0 100.0 ± 0.0 100.0 ± 0.0

(n = 25) (100.0, 100.0) (100.0, 100.0) (100.0, 100.0)

6months 96.0 ± 3.9 96.0 ± 3.9 88.0 ± 6.5

(n = 24) (88.6, 100.0) (88.6, 100.0) (76.1, 100.0)

1 year 86.4 ± 7.4 86.4 ± 7.4 68.8 ± 10.0

(n = 17) (73.1, 100.0) (73.1, 100.0) (51.8, 91.4)

1.5 years 59.8 ± 14.6 59.8 ± 14.6 39.6 ± 13.2

(n = 8) (37.1, 96.3) (37.1, 96.3) (20.7, 75.9)

SE standard error, IOP intraocular pressure; n number of eyes


undergone placement of a Boston keratoprosthesis type1 with a postoperative course complicated by endoph-thalmitis, chronic angle-closure glaucoma, and a

persistent corneal epithelial defect. The other eye withVA loss of > 2 lines underwent Descemet stripping epi-thelial keratoplasty after the tube insertion surgery due

Fig. 2 Kaplan-Meier survival curves of pars plana glaucoma drainage device insertion with pars plana vitrectomy using one of the vitrectomy portsites for tube placement. Success criteria were defined as the following: postoperative intraocular pressure (IOP) reduction ≥ 20% with IOP > 5mmHg and (a) IOP ≤ 21 mmHg; or (b) IOP ≤ 18mmHg; or (c) IOP ≤ 14mmHg without additional IOP-lowering glaucoma procedures or loss oflight perception vision. A failure was recorded on the latter visit if a patient failed to meet success criteria on two consecutive follow-up visitsafter 3 months


Table 4 Hazard ratios from univariate Cox proportional-hazard modeling using demographic and preoperative data

Parameter IOP reduction ≥ 20% with 5 < IOP ≤ 21mmHg

HR (95% CI) p value

Age 0.979 (0.931–1.031) 0.4

Sex (Female) 0.6

Male 0.619 (0.113–3.407)

Glaucoma stage (Indeterminate) 0.3

Mild 0.189 (0.011–3.367)

Moderate 0.331 (0.030–3.616)

Severe 0.066 (0.004–1.137)

Family history of glaucoma (No) 1.0

Yes 0.972 (0.097–9.784)

Type of glaucoma implant (AGI) 0.9

BGI 0.834 (0.094–7.364)

Vitrectomy cannula gauge 0.973 (0.175–5.408) 1.0

Preoperative IOP 0.864 (0.722–1.033) 0.1

Preoperative medication burden 0.465 (0.184–1.175) 0.1


HR (95% CI) p value

Age 0.979 (0.931–1.031) 0.4

Sex (Female) 0.6

Male 0.619 (0.113–3.407)


Mild 0.189 (0.011–3.367)

Moderate 0.331 (0.030–3.616)

Severe 0.066 (0.004–1.137)


Yes 0.972 (0.097–9.784)


BGI 0.834 (0.094–7.364)





HR (95% CI) p value

Age 0.987 (0.952–1.023) 0.5

Sex (Female) 0.1

Male 2.697 (0.771–9.438)


Mild 0.410 (0.035–4.753)

Moderate 0.751 (0.084–6.721)

Severe 0.228 (0.023–2.289)


Yes 0.431 (0.082–2.263)


BGI 0.397 (0.050–3.175)


to persistent corneal edema from aphakic bullous kera-topathy, which was present preoperatively.Cumulative success probabilities derived from Kaplan-

Meier analyses for all three success criteria are shown inTable 3, with corresponding Kaplan-Meier curvesdepicted in Fig. 2. For success defined as IOP ≤ 21mmHg or ≤ 18 mmHg (Criteria 1 and 2, respectively) asabove, success probabilities were both 86.4 ± 7.4% at 1year and 59.8 ± 14.6% at 1.5 years. For an even strictersuccess criteria of IOP ≤ 14mmHg (Criteria 3), successprobability was 68.8 ± 10.0% at 1 year and 39.6 ± 13.2% at1.5 years. Hazard ratios for age, sex, glaucoma stage,family history of glaucoma, type of glaucoma implant, vi-trectomy cannula gauge, preoperative IOP, or preopera-tive medication burden were not significant for anysuccess criteria and are listed in Table 4.Last follow-up visit outcomes are listed in Table 5.

Three eyes (10.7%) achieved complete success and 14eyes (50.0%) achieved qualified success under Criteria 1.Four eyes (14.3%) were a qualified failure and 7 eyes

(25.0%) required additional glaucoma surgery, as detailedbelow.Complication rates are shown in Table 6. The most

common complications prior to 3 months postopera-tively were anterior chamber (AC) inflammation in 13eyes (46.4%), corneal edema in 9 eyes (32.1%), andcystoid macular edema (CME) in 5 eyes (17.9%). Latecomplications after 3 months included CME in 5 eyes(20.8%), corneal edema in 3 eyes (12.5%), and AC in-flammation in 1 eye (4.2%). Seven of the 9 eyes withearly corneal edema developed corneal abrasions in-traoperatively that resolved prior to 3 months postop-eratively, and the remaining 2 eyes had preoperativecorneal edema with a history of penetrating kerato-plasty. These two eyes also had prolonged cornealedema postoperatively, which persisted through 6months postoperatively in one eye due to a combin-ation of Fuch’s dystrophy, aphakia, and preoperativevitreous prolapse and at 8 months postoperatively inthe second eye due to a persistent epithelial defect. Athird eye with prolonged corneal edema had aphakicbullous keratopathy at 9 months postoperatively re-quiring a Descemet stripping automated endothelialkeratopathy the following month. Five eyes had CMEafter surgery, which was present pre-operatively inthree eyes and resolved in one eye at 2 months, thesecond eye at 3 months, and the third eye at 9 monthspostoperatively. In the two remaining eyes, one eyedeveloped CME at 3 months, which resolved after 2months of topical steroid use. In the other eye, CMEdeveloped at 1.5 months and persisted through theirlast follow-up despite topical steroid use.Hypotony was noted in 1 patient (3.6%) and self-

resolved after 2 weeks. Vitreous hemorrhage was presentin three eyes prior to surgery and resolved with surgeryin two eyes. Vitreous hemorrhage was found in 4 eyespostoperatively and self-resolved after 2 weeks. One eyewith preoperative vitreous hemorrhage and one eye witha diagnosis of NVG but no preoperative vitreoushemorrhage received an intravitreal bevacizumab injec-tion one month prior to the combined PP GDD andPPV procedure. Two eyes (7.1%) required subsequentPPV for tube obstruction with vitreous or blood. Noeyes developed choroidal detachment, retinal tears, ret-inal detachment, endophthalmitis, or diplopiapostoperatively.

Table 4 Hazard ratios from univariate Cox proportional-hazard modeling using demographic and preoperative data (Continued)




IOP intraocular pressure, HR hazard ratio, CI confidence interval, AGI Ahmed glaucoma implant, BGI Baerveldt glaucoma implant

Table 5 Summary of intraocular pressure, medication burden,and visual acuity outcomes at the last follow-up visit forglaucoma patients who underwent pars plana glaucomadrainage device implantation with pars plana vitrectomy usingthe vitrectomy sclerotomy for tube insertion

IOP (mmHg) Medications VA (LogMAR)

Totala (n = 21)

Mean ± SD 12.0 ± 3.7 2.3 ± 1.4 0.79 ± 0.75

Range 6–20 0–4 0–3

Complete success (n = 3)

Mean ± SD 8.7 ± 1.5 0 ± 0 0.51 ± 0.05

Range 7–10 0 0.48–0.54

Qualified success (n = 14)

Mean ± SD 12.0 ± 3.9 2.4 ± 1.0 0.80 ± 0.80

Range 6–20 1–4 0.10–3

Qualified failure (n = 4)

Mean ± SD 14.8 ± 1.3 3.5 ± 0.6 0.89 ± 0.86

Range 13–16 3–4 0–2

IOP intraocular pressure, mmHg millimeters of mercury, VA visual acuity,LogMAR logarithm of the Minimum Angle of Resolution, n number of eyes, SDstandard deviationaExcluding eyes that underwent additional procedures after the initialcombined procedure and were categorized as failures


Seven patients had additional glaucoma surgeries after thecombined surgery. Two patients received a combination ofaugmented Micropulse transscleral cyclophotocoagulation(MP-TSCPC) [11] and continuous wave transscleral cyclo-photocoagulation at 15months and 16months respectively.Another two patients underwent MP-TSCPC at 2.5months,and one patient underwent MP-TSCPC at 8.2months.

Finally, one patient underwent PPV at 1month for vitreousoccluding the tube, and another patient underwent PPV at 2months for blood occluding the tube.

DiscussionThis study is the largest study to date that examines out-comes of pars plana GDD insertion through an existing

Table 6 Postoperative early and late complication rates for glaucoma patients who underwent pars plana glaucoma drainagedevice implantation with pars plana vitrectomy using the vitrectomy sclerotomy for tube insertion

N (%)

AC Inflammation Hypotony Corneal edema Cystoid macular edema Vitreous hemorrhage Tube obstruction

Total (n = 28) 14 (50.0) 1 (3.6) 9 (32.1) 5 (17.9) 6 (21.4) 2 (7.1)

Earlya (n = 28) 13 (46.4) 1 (3.6) 9 (32.1) 5 (17.9) 4 (14.3) 2 (7.1)

Lateb (n = 24) 1 (4.2) 0 (0.0) 3 (12.5) 5 (20.8) 0 (0.0) 0 (0.0)

N number of eyes in group, n total number of eyes, AC anterior chamberaComplications present up to 3months postoperatively, not including preoperative findingsbComplications present after 3 months postoperatively

Table 7 Selection of retrospective studies of pars plana glaucoma drainage device placement in a new sclerotomy separate fromthe vitrectomy sclerotomy sites

Author, year Tarantolaet al., 2011[15]

Shaikh et al.,2014 [16]

Varmaet al., 1995[17]

Sidoti et al., 2001 [18] Witmer et al., 2010 [19]

Publication Retina BMJ Ophthal AJO Ophthal J Glaucoma

Glaucoma type UncontrolledCACG

Mixed OAG andACG

Mixed Mixed

GDD type Baerveldt – Baerveldt Ahmed, Baerveldt, Molteno, Krupin Baerveldt

Sclerotomy fortube insertion

Different Different Different Different Different

PPV gauge 20(endoscope-assisted)

20, 23, 25(endoscope-assisted)

– – –

F/U (months) Mean 62(range 10–106)

Median 18 (range 12–28)

Mean 12.1 (range 0–31.8) Mean 38.4 (range 6–86)

# of eyes 19 13 13 34 51

% Complete /qualified successa

26 / 47 – – 47 / 41 –

IOP (mean preop/ final (mmHg))

31.3 / 11.4 23.0 / 12.0 35 / 13 17.9 / 15.1 26.9 / 13.5

# of Meds (meanpreop / final)

3.4 / 1.3 3.1 / 0.3 - / 0.8 – 3.2 / 1.1

# VA decline 1 (5.3%) – 4 (30.8%) 5 (15%) 16 (31.4%)

# eyes withcomplications

5 (26.3%) 0 (0%) – – 20 (30%)

Selectcomplications(%)

vTB – 5;sTB – 5; SR –5; hCD – 5

– LEM – 15 CGF – 50; H – 3; CD – 12; CME – 3; RD – 6; vTB– 9; bTB – 3; VH – 6; U – 6; Hy – 3; ScH – 6

I – 10; RD – 6; D – 6; vTB –4; H – 4; ERM – 4; CEf – 4

# of glaucomareoperations

5 (26.3%) 3 (23.1%) 2 (15.4%) – –

CACG chronic angle closure glaucoma, OAG open angle glaucoma, ACG acute-closure glaucoma, vTB vitreal tube blockage, sTB swollen Soemmering’s ringblocking tube, SR shunt retraction, CD choroidal detachment, hCD hemorrhagic choroidal detachment, LEM limited eye movement, D diplopia, vTB vitreal tubeblockage, H hypotony, as defined by IOP < 6mmHg; ScH suprachoroidal hemorrhage, Hy hyphema, CGF corneal graft failure, U uveitis, ERM epiretinal membrane, Iiritis, CEf choroidal effusion, CME cystoid macular edema, RD retinal detachmentaComplete success was defined as IOP between 6 and 21mmHg without medications. Qualified success was defined as IOP between 6 and 21mmHgwith medications


vitrectomy sclerotomy site. In this study, the mean IOPand medication burden were significantly reduced at allpostoperative time points compared to preoperativelevels. Three eyes achieved complete success and 14 eyesachieved qualified success at their last follow-up visit, fora total success rate of 60.7% (17/28 eyes) under Criteria1. This success rate is slightly lower than total successrates reported by prior studies ranging from 67 to 100%,as seen in Tables 7, 8, and 9. However, given that ourmean preoperative IOP was lower than that of otherstudies, our lower success rate may instead potentiallyreflect a lower magnitude of IOP reduction secondary toa lower starting IOP. Vitrectomy gauge was not a

predictive factor for failure, as demonstrated by the non-significant hazard ratio. Average visual acuity was un-changed from preoperative levels at all follow-up visitsafter POD1, and two patients experienced > 2 lines ofvisual acuity loss due to corneal problems as previouslydescribed in our results. Overall, the final postoperativeIOP, postoperative medication burden, and visual acuityfindings in this study were similar to prior studies evalu-ating outcomes of combined pars plana GDD insertionand vitrectomy (Tables 7, 8, and 9).The most common complication encountered in this

study was transient anterior chamber inflammation in13 out of 28 eyes (46.4%), which resolved in all cases

Table 8 Selection of retrospective studies of pars plana glaucoma drainage device placement in either a new sclerotomy or existingvitrectomy sclerotomy site

Author, year de Guzman et al., 2006[20]

Qinet al.,2018[21]

Kolomeyer et al., 2015 [6] Kolomeyer et al.,2012 [22]

Kaynaket al., 1998[23]

Luttrull et al.,2000 [24]

Publication Clin Exp Ophthal JGlaucoma

Retina Oman J Ophthal Br J Ophthal Ophthal

Glaucomatype

Mixed Mixed NVG Mixed Mixed (noNVG)

Mixed

GDD type Baerveldt, Molteno Ahmed,Baerveldt

Baerveldt Baerveldt Molteno Baerveldt

Sclerotomyfor tubeinsertion

Both Both Both Both Unspecified Unspecified

PPV gauge – – 20, 23, 25 20, 23 – –

F/U (months) Mean 30.2 (range 6–77) Mean43.5

Mean 19.9 (range 2–66) Mean 33.7 Mean 30.3(range 4–71)

Mean 18 (range3–41)

# of eyes 33 57 89 39 17 50

% Complete /qualifiedsuccessa

49 / 42 – 30 / 37 21 / 54 – 56 / 28

IOP (meanpreop / final(mmHg))

33.1 / 13.4 29.0 /15.1

37.2 / 15.9 31.9 / 13.2 – 44 / 14

# of Meds(mean preop /final)

3.6 / 0.6 2.9 / 1.1 2.8 / 1.21 3.8 / 1.7 – 3.2 / 0.6

# VA decline 13 (39.4%) 22(38.6%)

34 (38%) 14 (36%) 2 (11.8%) 14 (28%)


– 16(28.1%)

8 (47.1%)

Selectcomplications(%)

VH/H – 12; CD – 27; CE – 30;U – 3; LEM – 3; CGF – 15;vTB – 6; iTB – 3; ERM – 3; CEf– 3

D – 16; H– 9; VH –2; TE – 2

OH – 92; H – 22; Hy – 21; CE –19; VH – 16; CME – 15; CD – 12;RD – 4; TB – 3; En – 3; SrH – 1;ERM – 2

H – 23; CD – 26;OH – 13; RH – 10;VH – 5; CME – 5;ERM – 5

H – 12; VH –6; CD – 6; RD– 12; CED –29

CEf – 36; CME– 4; D – 6; RD –8; CH – 4; VH –2


13 (39.4%) 8 (14.0%) 9 (10%) 5 (13%) 1 (5.9) –

NVG neovascular glaucoma, VH vitreal hemorrhage, CD choroidal detachment, CE corneal edema, U uveitis, LEM limited eye movement, CGF corneal graft failure,vTB vitreal tube blockage, iTB iris blocking tube, ERM epiretinal membrane, CEf choroidal effusion, D diplopia, H hypotony, as defined by IOP < 6mmHg; TE tubeerosion, OH ocular hypertension, Hy hyphema, RD retinal detachment, TB tube blockage, En endophthalmitis, SrH subretinal hemorrhage, RH retinal hemorrhage,CED corneal endothelial decompensation, CEf choroidal effusion, CH choroidal hemorrhageaComplete success was defined as IOP between 6 and 21mmHg without medications. Qualified success was defined as IOP between 6 and 21mmHgwith medications


after 2 weeks except for one eye, where inflammationwas present intermittently and resolved after 1 year. Cor-neal edema was present in 2 eyes preoperatively and de-veloped in 7 eyes postoperatively. Edema was present in3 eyes by 6 weeks and resolved in all eyes after 1 year.Corneal edema was most commonly due to cornealabrasions acquired during surgery, although a compo-nent of prolonged surgical insult from the combinedPPV and GDD surgeries may also have contributed. Pro-longed corneal edema has also been shown to resultfrom PPV alone [12, 13]. These complication rates werecomparable to that of prior studies, as seen in Tables 7,8, and 9.Previously, GDD tube insertion in an existing vitrec-

tomy sclerotomy was thought to result in a higher riskof hypotony due to aqueous leakage around the tube,particularly when sclerotomies larger than 21-gaugewere used for vitrectomy [3, 6]. Scott et al. [3] demon-strated a higher incidence of hypotony in their eyes withGDD tubes inserted into sclerotomies created by 20-gauge needles (0/8 eyes) compared to 23-gauge needles(5/18 eyes, 28%). In a study of neovascular glaucoma pa-tients, Kolomeyer et al. [6] also noted a significantly

higher rate of transient hypotony in 20-gauge versus 23-or 25-gauge PPV eyes (p = 0.021), with tube insertioninto an existing sclerotomy for the 23- and 25-gaugePPV. In comparison, for 25-gauge PPV, Reichstein et al.[7] found no hypotony amongst the 10 eyes studied alsowith GDD tube placement in a vitrectomy sclerotomy.In our study, hypotony was noted in 1 eye (3.6%) andself-resolved after 2 weeks, similar to the low rates of hy-potony noted in prior studies with small-gauge PPV re-gardless of sclerotomy status. Thus, tube insertion in anexisting sclerotomy site from 23- or 25-gauge PPV mayresult in a lower risk of hypotony compared with 20-gauge PPV, and creating an additional sclerotomy forthe GDD tube may not be necessary.Vitreous hemorrhage was found in a total of 6 eyes

(21.4%) and was present in 3 eyes prior to surgery. Threeadditional eyes developed vitreous hemorrhage postoper-atively, which resolved after 2 weeks. Of the eyes thathad vitreous hemorrhage preoperatively, two resolvedwith surgery, and one resolved after 2 weeks. Two eyes(7.1%) experienced tube occlusion with either blood orvitreous requiring subsequent PPV. These findings of a12% (3/25 eyes) incidence of vitreous hemorrhage are

Table 9 Selection of retrospective studies of pars plana glaucoma drainage device placement in an existing vitrectomy sclerotomysite

Author, year Reichstein et al.,2011 [7]

Kolomeyer et al., 2012 [5] Present study

Publication Ophthal Eur J Ophthal –

Glaucoma type Mixed Mixed Mixed

GDD type Ahmed, Baerveldt Baerveldt Ahmed, Baerveldt

Sclerotomy for tubeinsertion

Same Same Same

PPV gauge 25 23 23, 25

F/U (months) > 12 Mean 12.1 (range 6–27) Mean 14.2 (range 3.1–35.5)

# of eyes 10 8 28

% Complete / qualifiedsuccessa

– 25 / 75 14 / 46

IOP (mean preop / final(mmHg))

31 / 16.1 29.1 / 13.8 22.8 / 11.8

# of Meds (mean preop /final)

2.5 / - 3.9 / 1.9 4.3 / 2.0

# VA decline 3 (30%) 3 (37.5%) 7 (25%)


– – 14 (50%)

Select complications (%) CE – 20 H – 38; DR – 25; VH – 13; IRH – 25; CE – 13; CH– 13; CD – 25

ACI – 50; H – 4; CE – 32; CME – 18; VH – 21;vTB – 4; bTB – 4


0 (0.0%) 1 (12.5%) 6 (21.4%)

CE corneal edema, H hypotony, as defined by IOP < 6mmHg; DR decompression retinopathy, VH vitreal hemorrhage, IRH intraretinal hemorrhage, CH choroidalhemorrhage, CD choroidal detachment, ACI anterior chamber inflammation, vTB vitreal tube blockage, bTB blood tube blockageaComplete success was defined as IOP between 6 and 21mmHg without medications. Qualified success was defined as IOP between 6 and 21mmHgwith medications


within the range of findings from prior studies of PPGDD placement and PPV (Tables 7, 8, and 9). A higherincidence of vitreous hemorrhage has also been noted instudies of patients with neovascular glaucoma, withKolomeyer et al. [6] reporting 14 out of 89 eyes (16%)and Campagnoli et al. [14] reporting 25 out of 43 eyes(58.1%) with vitreous hemorrhage on postoperative day1 persisting through 1 year in 16 eyes.The postoperative prevalence of CME was slightly

higher in our study than in prior studies. Five eyes(17.9%) had CME postoperatively with resolution in 3eyes prior to 1 year. However, given that 3 eyes hadpre-existing CME prior to surgery, the true incidenceof CME within our study is 2 out of the 23 at-riskeyes in our cohort (8.7%), congruent with resultsfrom prior studies of pars plana GDD insertion andvitrectomy demonstrating rates between 3 to 15%(Tables 7, 8, and 9). Given that Massachusetts Eyeand Ear is a tertiary-care center and that 3 of the 5eyes with postoperative CME had CME preopera-tively, it is possible that the patients in our studywere sicker and more complex than patients at non-tertiary-care centers, potentially resulting in ourhigher prevalence of CME compared to other studies.Other retinal complications from pars plana vitrec-tomy, including retinal detachment, retinal tears, andretinal dialyses, were not observed in our study.Limitations of this study include its retrospective de-

sign, small sample size, lack of a comparison group oftube insertions in a separate sclerotomy, large numberof surgeons, and short follow-up time period for patientswho had undergone surgery more recently, particularlyas expected follow-up visits were displaced by COVID-19. This study is likely not generalizable to surgeriesthat were not Ahmed valves or if the implant wereplaced in a location other than the superotemporalquadrant. As children were not included in our study,this study is not applicable to that population. Smallersample sizes at later time points may have affectedthe significance of statistical testing. Given that mul-tiple glaucoma and retina surgeons performed theprocedure, it is less likely that bias from a single sur-geon affected the results of our study; however, thevariability in surgical technique may affect our results.Despite extensive efforts to identify a comparisongroup with tube insertions in a new sclerotomy separ-ate from the vitrectomy sclerotomy sites, we couldnot identify a sufficient number of cases to form asuitable comparison group for this study. Thus, werelied on comparisons with prior studies of pars planaGDD insertion and vitrectomy to evaluate our results.Finally, there may be a referral bias as patients in ourstudy were treated at a tertiary-care center, whichmay limit the generalizability of our results.

ConclusionsIn summary, our results demonstrate that inserting aGDD tube into an existing vitrectomy sclerotomy siteduring combined pars plana GDD insertion and small-gauge vitrectomy likely does not increase the risk ofcomplications. Specifically, there does not appear to bean increased risk of hypotony through leakage aroundthe tube when an existing vitrectomy sclerotomy is uti-lized. We found similar functional outcomes and com-plication risk compared to prior studies of the samecombined surgery, regardless of tube placement in exist-ing or new sclerotomies. Minimizing the number ofsclerotomies created during surgery may potentially re-duce the risk of hypotony or tissue trauma and decreaseoperative time. Thus, GDD placement in a vitrectomysclerotomy can be safely considered in cases that utilizesmall-gauge pars plana vitrectomy.

AbbreviationsPP: Pars plana; GDD: Glaucoma drainage device; PPV: Pars plana vitrectomy;IOP: Intraocular pressure; BCVA: Best-corrected visual acuity; VA: Visual acuity;POD1: Postoperative day 1; POW2: Postoperative week 2;POW6: Postoperative week 6; POM3: Postoperative month 3;POM6: Postoperative month 6; POY1: Postoperative year 1;POY1.5: Postoperative year 1.5; CME: Cystoid macular edema; NLP: No lightperception; SD: Standard deviation; LogMAR: Logarithm of the minimumangle of resolution; MP-TSCPC: Micropulse transscleral cyclophotocoagulation

AcknowledgementsWe would like to acknowledge Cameron Neeson for her assistance inproofreading this manuscript and Nathan Hall for his advice regardingstatistical testing. We also gratefully appreciate Mr. Chad Gifford, Mrs. AnneGifford, Mr. Joseph Leitch, Mrs. Cathey Leitch, and Mr. Stephen Traynor fortheir philanthropic support of this work.

Authors’ contributionsEKC was involved in project design, data collection, analysis, and manuscriptdrafting and revision. SG and MC assisted with data collection andmanuscript drafting. JBM and TCC were involved in project design andmanuscript drafting, and DS was involved in project design, analysis,manuscript drafting, and revision. All authors read and approved the finalmanuscript.

FundingNo funding outside of the philanthropic support mentioned above wasobtained for this project.

Availability of data and materialsThe data that support the findings of this study are available on requestfrom the corresponding author DS. The data are not publicly available dueto them containing information that could compromise research participantprivacy.

Ethics approval and consent to participateThis retrospective chart review study was approved for exempt status by theMass General Brigham Institutional Review Board and abided by the tenetsof the Declaration of Helsinki. Informed consent was not required forparticipation.

Consent for publicationConsent for publication was not required.

Competing interestsThe authors declare that they have no competing interests.


Author details1Massachusetts Eye and Ear, Department of Ophthalmology, Harvard MedicalSchool, Boston, MA, USA. 2Massachusetts Eye and Ear, Department ofOphthalmology, Boston, MA, USA. 3Bascom Palmer Eye Institute, Miami, FL,USA.

Received: 27 September 2020 Accepted: 17 February 2021

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